1. Field of the Invention
The present invention is directed to an x-ray diagnostic apparatus, particularly for cardioangiography, having an x-ray source and an x-ray image intensifier/video chain or other x-ray image converters, wherein the x-ray source and the x-ray image intensifier are cyclically moved during the production of a number of successive images.
2. Description of the Prior Art
An x-ray diagnostic apparatus of this type is disclosed, for example, by German PS 44 13 458, wherein difference images are produced in the pathfinder technique for better spatial visibility in certain device settings, with the x-ray diagnostic apparatus being is cyclically moved.
xe2x80x9cdynavisionxe2x80x9d exposure series is usually made of a resting subject during a contrast agent injection for the currently standard 3D reconstruction of angio systems, with an exposure series over an angular range of xe2x89xa7180xc2x0 of the subject ensuing by means of a rotating C-arm.
A 3D reconstruction of the selected subject region ensues from this series according to a specific reconstruction algorithm.
The desired view can then be selected for observation with the assistance of various presentation modes, for example MIP (maximum intensity projection) or VR (volume rendering).
A prerequisite for a successful 3D reconstruction is that the subject be at rest and, in the case of angiography, an adequately long and uniform contrast agent display, so that such 3D angiography reconstructions can currently be employed only for the presentation of vessels in the skull.
However, it would also be diagnostically important to be able to portray vessels with greater movement in angio systems with 3D reconstruction, particularly coronary arteries, wherein it is especially the morphology, i.e. the anatomical modifications, for example of a stenosis, that are of critical diagnostic significance.
At first glance, however, it would seem a 3D reconstruction is practically impossible in cardioangiography. The heartbeat constantly changes the position of the vessels in the x-ray image, so thatxe2x80x94purely theoreticallyxe2x80x94the exposures for the dynavision scene could only be made given EKG-triggered image sequence control and an extremely long bolus, which, however, is completely out of the question for health reasons.
An object of the present invention is to provide an x-ray diagnostic apparatus of the type initially described which can also be utilized in cardioangiography.
For achieving this object, it is inventively provided that the motion of the vessel due to the heartbeat is compensated with a xe2x80x9ccardiac motion compensationxe2x80x9d in a small image region having an abnormality to be investigated, particularly a stenosis.
An important, basic idea of the invention is the limitation of the 3D reconstruction to an extremely small image region, namely specifically that of the stenoses, i.e. of the constrictions of the vessels. In an embodiment of the invention, the vessel is acquired in the selected, small image excerpt by a center line detection and is retained on a point of the image. Views of the stenosis thus arise from different observation angles dependent on the respective position of the C-arm in the dynavision, rotational movement.
The further-processing and the 3D reconstruction have an especially simple form when the vessel acquired by the center line detection and retained on a point of the image is xe2x80x9cbent straightxe2x80x9d by a computer in the retained image excerpt, so that a 3D reconstruction of the selected image area from the digitized data of successive images of an image sequence only ensues subsequently with a reconstruction algorithm.
It is within the scope of the invention for this central region of the image to be employed as a virtual isocenter for the 3D reconstruction. A geometrical distortion correction (x-ray image intensifier, beam path, etc.) is eliminated since the image region is extremely small. At the end of the calculation, the image region with the stenosis as a 3D image is available as an image result and provides information about the existing morphology. A better estimate of the therapeutic measures is thus possible, for example balloon angioplasty, laser treatment, bypass operation, etc.